We have discovered that the natural insecticide, Rotenone, induces a high incidence of mammary tumors in the albino rat. In the first year of work, we discovered that rotenone tumors have a morphology very similar to the mammary tumors of the human female and that rotenone tumors are transplantable and are inducible per oral administration. We also defined that rotenone tumors have characteristic structural and biochemical alterations of mitochondria. In this second year of work, we have found that the possible pathogenic mechanism of the induction of tumors with rotenone is the following: rotenone administration -elevation of cerebral glutamate - possible hypothalmic alteration -possible evaluation of somatotrophin and gonadotrophin and elevation of prolactin - elevation of estrogens, progesterones and somatomedins. Additionally, we have made an epidemological study which demonstrates that rotenone reaches and is ingested by American citizens (in food and water), the levels being, for example, 20 ug per gram of green beans. Other biochemical studies were also performed. BIBLIOGRAPHIC REFERENCES: M. Gosalvez, J. Diaz-Gil, J. Coloma and L. Salganicoff. Spectral and metabolic characteristics of mitochondrial fractions isolated from rotenone tumors. J. Natl. Canc. Institute, March, 1976, in press.